This application is based on Japanese Patent Application No. 11-097052 (1999) filed Apr. 2, 1999, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a printing apparatus and a printing registration method, and more specifically this invention seeks to simplify the construction for printing registration during performing printing in the bi-directions of a forward scan and a reverse scan of a printing head and/or for alignment among printing heads during performing printing using a plurality of printing heads.
2. Description of the Related Art
Conventionally, printing registration in a printing apparatus for forming images by dots has generally been performed as described below.
For example, in the case of printing registration in a forward scan and a reverse scan, relative printing registration conditions for the forward scan and the reverse scan are changed by adjusting the printing timing for the forward scan and for the reverse scan to perform bi-directional scanning in their respective printing registration conditions, thereby printing ruled lines on a printing medium. Then a person such as a user observes the printed results and selects the printing conditions leading to the best registration, thereby setting the printing conditions for registration in a device such as a printing apparatus or a host computer.
In performing registration among heads in the case of a printing apparatus having a plurality of heads, relative printing registration conditions are changed, and ruled lines are printed by means of respective heads, then similarly to the manner mentioned above, a person such as a user selects the conditions leading to the best registration, thereby establishing the printing registration conditions in a device such as a printing apparatus or a host computer.
However, in the case of such a printing registration processing method, complexity is involved in that the user is required to visually observe the printed results, to select the optimum dot-depositing registration conditions, and to carry out data entry operation. Furthermore, fundamentally, because a judgment for obtaining the optimum printing position by observing through human eyes is required by the user, the optimum registration is not necessarily set. Therefore, it is especially unfavorable to the user who is not accustomed to such operation.
Moreover, the user is enforced to expend in time and effort at least two times since the user should print the image to perform the depositing registration and, in addition, to perform conditional establishment after observing the user must perform judgments, whereby upon realizing the apparatus or system is excellent in operability, it is not only undesirable but also is disadvantageous from the viewpoint of time consumption.
In Japanese Patent Application Laid-Open No. 10-329381 (1998), the present applicant proposed an improved method whereby a device or a system capable of printing high-speed and high-quality images without causing any such operational problems is realized at a low cost.
The system under this improved method in a printing apparatus for performing printing on a printing medium by using a printing head comprises means for controlling the printing head to form a plurality of patterns, the plurality of patterns being respectively formed corresponding to a plurality of shifting amounts of relative printing positions of a first printing and a second printing to be registered and the plurality of patterns respectively having optical characteristics corresponding to the plurality of shifting amount, means for measuring respective optical characteristics of the plurality of the formed patterns, and means for performing printing registration processing between the first printing and the second printing on the basis of the respective optical characteristics of a plurality of patterns measured by the optical characteristics measurement means.
This invention intends to simplify the construction for performing such printing registration. Specifically, an object of the present invention is to avoid addition of a sensor to be used in the means for measuring optical characteristics during the printing registration operation which is considered to be applied with a relatively little use frequency, and thereby to restrain the resulting rise of the production cost of the printing apparatus.
Furthermore, another object of the present invention is to restrain the complexity of the construction of the peripheral circuits which results from the increase of the number of sensors installed in the printing apparatus, namely to restrain factors such as the increase of the number of amplification circuits, reference voltage circuits, and input ports connected to sensors, thereby conducing to a reduction of the cost of printing apparatuses capable of performing printing registration.
In a first aspect of the present invention, there is provided a printing apparatus for performing printing on a printing medium by using a printing head, comprising:
means for controlling the printing head to form a plurality of patterns, the plurality of patterns being respectively formed corresponding to a plurality of shifting amounts of relative printing positions of a first printing and a second printing to be registered and the plurality of patterns respectively having optical characteristics corresponding to the plurality of shifting amounts;
optical measuring means for measuring respective optical characteristics of the plurality of patterns;
means for performing printing registration processing between the first printing and the second printing on the basis of the respective optical characteristics of the plurality of patterns measured by the optical measuring means; and
means for performing a detecting operation distinct from the measurement of the optical characteristics by using the optical measuring means.
In a second aspect of the present invention, there is provided a printing apparatus for performing printing on a printing medium by a first printing and a second printing by using a printing head, comprising:
means for measuring respective optical characteristics of a pattern used for performing a printing registration between the first printing and the second printing; and
means for performing a detecting operation distinct from the measurement of the optical characteristics by sing the measuring means.
In a third aspect of the present invention, there is provided a printing registration method for a printing apparatus for performing printing on a printing medium by using a printing head, the method comprising the steps of:
controlling the printing head to form a plurality of patterns, the plurality of patterns being respectively formed corresponding to a plurality of shifting amounts of relative printing positions of a first printing and a second printing,to be registered and the plurality of patterns respectively having optical characteristics corresponding to the plurality of shifting amounts;
measuring the respective optical characteristics of the plurality of patterns by using optical measuring means;
performing printing registration processing between the first printing and the second printing on the basis of the respective optical characteristics of the plurality of patterns measured by the optical measuring means; and
performing a detecting operation distinct from the measurement of the optical characteristics by using the optical measuring means.
In a fourth aspect of the present invention, there is provided a printing registration method for a printing apparatus for performing printing on a printing medium by a first printing and a second printing by using a printing head, comprising:
measuring respective optical characteristics of a pattern used for performing a printing registration between the first printing and the second printing by using optical measuring means; and
performing a detecting operation distinct from the measurement of the optical characteristics by using the optical measuring means.
In a fifth aspect of the present invention, there is provided a printing system provided with a printing apparatus for performing printing on a printing medium by using a printing head, and a host apparatus for supplying image data to the printing apparatus, comprising:
means for controlling the printing head to form a plurality of patterns, the plurality of patterns being respectively formed corresponding to a plurality of shifting amounts of relative printing positions of a first printing and a second printing to be registered and the plurality of patterns respectively having optical characteristics corresponding to the plurality of shifting amounts;
optical measuring means for measuring respective optical characteristics of the plurality of patterns;
means for performing printing registration processing between the first printing and the second printing on the basis of the respective optical characteristics of the plurality of patterns measured by the optical measuring means; and
means for performing a detecting operation distinct from the measurement of the optical characteristics by using the optical measuring means.
In the construction of the present invention, only the required functions are added without requiring any new sensors to be added, for example, by executing frequently used functions and infrequently used functions with a single sensor used in common and by using the sensor for each individual operating mode of the printing apparatus on a time division basis. Moreover, it is made possible using the same sensor to exhibit different characteristics by switching control such that the optimum sensor function for each operating mode is activated.
Incidentally, hereafter, the word xe2x80x9cprintxe2x80x9d (hereinafter, referred to as xe2x80x9crecordxe2x80x9d also) represents not only forming of significant information, such as characters, graphic images or the like but also represents forming images, patterns and the like on the printing medium irrespective of whether they are significant or not and whether the formed image is to be visually perceptible or not, in a broad sense, and further includes the case where the medium is processed.
Here, the wording xe2x80x9cprinting mediumxe2x80x9d represents not only paper typically used in the printing apparatus but also cloth, plastic film, a metal plate and the like and any substance which can accept the ink in broad sense.
Furthermore, the wording xe2x80x9cinkxe2x80x9d has to be understood in broad sense similarly to the definition of xe2x80x9cprintxe2x80x9d and should include any liquid to be used for formation of image patterns and the like or for processing of the printing medium.
In this specification, optical density, that is to say, reflection optical density using reflection factor or transmission optical density using transmission coefficient, is used as optical characteristics. However, optical reflection factor and reflected light intensity can also be used. In this specification, the term of xe2x80x9creflection optical densityxe2x80x9d is abbreviated to xe2x80x9coptical densityxe2x80x9d or simply to xe2x80x9cdensityxe2x80x9d except for confusion.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.